Method and device for baking food

ABSTRACT

A method pertaining to the baking of products (B) in a baking oven (1) in which the products are supported by at least one rotary oven trolley (17) comprises rotating the trolley through a number of revolutions in one direction (R1) during the baking process, and thereafter reversing the direction of rotation and continuing rotation of the trolley through several revolutions in the opposite direction (R2) before again reversing the direction of rotation of the trolley. The trolley (17) keeps the same axial position in both directions of rotation. An arrangement for carrying out the method includes a drive device (20-26) for alternating rotation of the oven trolley through an equal number of revolutions in both directions during the baking process.

TECHNICAL FIELD

The present invention relates to the baking of products in a bakingoven, more particularly an oven of the kind in which the products aresupported by at least one rotary oven trolley.

DESCRIPTION OF THE BACKGROUND ART

It is known, and generally common practice, to bake bread, buns, etc.,in an oven wherein the bread, buns, etc., are supported in tiers on ovenplates or oven sheets carried by an oven trolley which can be moved intoand out of the oven. The trolley can be connected to floor-mounted orceiling-mounted drive means for rotating the trolley slowly about itsvertical centre axis. The trolley is rotated to obtain more uniformbaking of the product, therewith obtaining a product of better qualitythan would otherwise be the case.

A baking oven of this kind is known from SE 395 595 and EP 112 786. Whenthe trolley is to be removed from the oven, The rotational direction ofthe trolley is reversed so as to lower or lift the trolley in theprocess of removing the same. The trolley rotates in one directionduring the actual baking process.

SUMMARY OF THE INVENTION

An object of the present invention is to improve still further thebaking result in ovens provided with rotary trolleys. This object isachieved with the inventive method and inventive arrangement having thecharacteristic features set forth in the characterizing clauses ofrespective independent claims.

This reversal of the direction of trolley rotation further improves theevenness to which the product is baked. In the aforesaid patentpublications, reversal of trolley rotation is effected during the bakingprocess and is not effected with the aim of obtaining an improved bakingresult as a result of such reversal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a baking oven provided with an arrangementaccording to the present invention;

FIG. 2 illustrates the oven in FIG. 1 from above;

FIG. 3 is a longitudinal sectioned view of the oven shown in FIG. 1,taken on the line III--III; and

FIG. 4 is a cross-sectional view of the oven shown in FIG. 1, taken onthe line IV--IV.

DESCRIPTION OF PREFERRED EMBODIMENTS

There is shown a baking oven 1 which has two side walls 2 and 3, a backwall 4, a front wall 5, a door 6 fitted to the front wall, a roof 7 anda bottom 8. All parts 2-7 are heat insulated. The oven 1 furtherincludes a ceiling 9, an inner wall 10, and two perforated inner walls11 and 12. Mounted in the spaces between the walls 3, 12 and 10, 11 is arespective steam pack 13 and 14 which function to moisten the air withinthe oven, with hot steam. Mounted in the space between the oven roof 7and the inner wall 9 is a fan 15 which forces the air in the oven 1 toflow in the paths illustrated by arrows in FIG. 1. A heat pack 16 forheating oven air is mounted between the side wall 2 and the inner wall10. Connections to respective steam packs 13, 14, fan 15 and heat pack16 have not been shown in the drawings since they are not required inobtaining an understanding of the invention. This also applies toventilation openings.

An oven trolley 17 having wheels 18 that can also be rotated in thehorizontal plane is shown inserted into the oven. The oven trolley 17includes a frame which supports a plurality of baking sheets 19. FIG. 3shows buns B placed on sheets 19. Mounted centrally in the upper part ofthe trolley 17 is a suspension roller 21. The roller 21 can be hookedonto a hook 20 which is connected to a shaft 22 that extends through theroof 7 and there connected to an electric motor 23 through the medium ofa belt pulley 22a, which is fixedly mounted on the shaft 22, a toothedbelt 24, a gear housing 25, and a toothed belt 26.

The motor 23 is reversible and is connected to a pulse counter 27 whichcounts the number of revolutions made by the motor 23 and when reachinga predetermined number of revolutions sends a pulse to the motor 23 andtherewith cause the motor to rotate in the opposite. The pulse counter27 is therewith set to zero and again begins to count the number ofrevolutions made by the motor 23 in this reversed direction. Subsequentto counting the same predetermined number of revolutions, the counter 27sends a pulse to the motor 23, causing the direction of rotation to beagain reversed.

Rotation of the motor 23 causes the oven trolley 17 to rotate about itsvertical centre axis at a predetermined speed. Reversal of the directionof rotation of the motor 23 will also result in reversal of thedirection of rotation of the oven trolley 17. It has been found suitableto reverse the direction of motor rotation subsequent to having rotatedthe oven trolley 17 through 2-15 revolutions, preferably about 5revolutions, in each direction.

It will be understood that any other suitable counter may be used as analternative to the pulse counter 27, such as a revolution counter, whichis actuated by the shaft 22, for instance, and which causes the motor toreverse its direction of rotation subsequent to the shaft, and therewiththe trolley 17, having rotated a predetermined number of revolutions.Alternatively, the motor 23 can be connected to a timing clock whichfunctions to cause the motor 23 to change its direction of rotationsubsequent to the passage of a predetermined time period, for instance100 seconds, that has been set on the clock.

A motor which rotates in only one direction can be used as analternative to a reversible motor 23, wherein there is arranged betweenthe motor and the shaft 22 a mechanism which is actuated by impulsesfrom, e.g., a pulse counter or a timing clock to reverse the rotationaldirection of the shaft 22.

The air heated by the heat pack 16 passes through the fan 15 and isforced downwards between the walls 3 and 12, where it is moistened bythe steam pack 13, said pack normally delivering steam once on eachbaking occasion. The space between these walls constitutes the pressureside of the oven. The air is then forced through the holes in the wall12 and passes between the sheets 19 carried by the rotating oven trolley17, such as to bake the buns B. The air then passes through the holes inthe wall 11 and is moistened by the steam pack 14, once with each bakingoccasion. The air then flows up between the walls 2 and 10, towards theheat pack 16. the space between the walls 11 and 2 constitutes thesuction side of the oven.

FIG. 4 shows from above a sheet 19 and a plurality of buns B supportedthereby. The buns located furthest out in two corners are designated B1and B2.

If it is assumed that the trolley 17 rotates in one single direction R1,that the peripheral speed of each bun B1, B2 will be V2, and that thehot, moist air passes between the sheets 19 at a speed of V1, then thebun B1 will be impinged upon at an air speed of V1+V2, whereas the bunB1 will be impinged upon at an air speed of V1-V2. This means that thebun B1 will be subjected to relatively large quantities of hot air withthe result that the bun will be baked noticeably on the side thereofwhich faces forwardly in the direction of rotation. When the bun B1reaches the position earlier occupied by the bun B2, the bun B1 will besubjected to relatively small quantities of hot air and the oppositeside of the bun B1 will therefore be baked to a lesser extent. Thismeans that one side of the bun B1 will either be baked sufficiently orexcessively, and that its other side is insufficiently or sufficientlybaked as the oven trolley rotates in one direction over a large numberof revolutions. This naturally applies to all buns B on the sheets 19.

On the other hand, if the trolley 17 rotates in alternate directionsthrough one and the same number of revolutions, the buns B will be bakedequally on both sides. When the peripheral speed V2 of the buns B1 andB2 and the air speed V1 are equally as great in both directions ofrotation R1 and R2, one side of each bun B1 and B2 will be impinged uponat an air speed of (V1+V2+(V1-V2) in the direction R1, and the oppositeside of the same bun will be impinged upon at an air speed of(V1-V2+(V1+V2) in direction R2. These air speeds are mutually identical,meaning that the air flowing between the sheets will have the sameeffect on both sides of the buns B when the trolley 17 rotates throughthe same number of revolutions in each rotational direction, andtherewith provide a uniform baking result.

Although the invention has been described and illustrated with referenceto only one embodiment together with some alternatives, it will beunderstood that the invention is not restricted hereto and that theinvention is only limited by the scope of the following claims.

We claim:
 1. A method of baking food (B) in an oven (1) in which thefood is supported by at least one rotary oven trolley (17), the methodcomprising the steps of rotating the trolley (17) through at least partof one revolution in a first direction (R1), then reversing therotational direction, then rotating the trolley (17) through at leastpart of one revolution in a second and opposite direction (R2), thenreversing the direction of rotation again, wherein rotation in both thefirst and second directions and the reversals in rotational directionstake place during the baking process, and wherein the oven trolleyretains the same axial position during rotation in both the first andsecond directions.
 2. A method according to claim 1 wherein the steps ofrotating the trolley through at least part of one revolution in thefirst direction, then reversing the rotational direction, then rotatingthe trolley through at least part of one revolution in the seconddirection, then reversing the direction of rotation again togethercomprise rotation in the first direction (R1) through the same number ofrevolutions as rotation in the second direction (R2).
 3. A methodaccording to claim 1 wherein the steps of rotating the trolley throughat least part of one revolution in the first direction, then reversingthe rotational direction, then rotating the trolley through at leastpart of one revolution in the second direction, then reversing thedirection of rotation again together comprise rotating the oven trolleyin one of the first and second directions (R1, R2) through 2-15revolutions.
 4. An arrangement for baking food (B) in a baking oven (1)in which the food is supported by at least one rotary oven-trolley (17),wherein the oven has a pressure side from which hot air flows towardsthe trolley, and an opposing suction side to which air flows afterheating the food, and wherein the arrangement includes drive means(20-26) for rotating the trolley in a first direction, means foractuating the drive means to reverse the direction of rotation of thetrolley to rotate the trolley in a second and opposite direction duringthe baking of the food in the baking oven; and wherein the oven trolleyretains the same axial position in both the first and second directionsof rotation.
 5. An arrangement according to claim 4 wherein the drivemeans (20-26) includes a motor (23) mounted on one of the oven roof (7)and the oven floor (8).
 6. An arrangement according to claim 5 whereinthe motor (23) is a reversible motor.
 7. An arrangement according toclaim 4 further comprising means (27) for causing the drive means(20-26) to reverse the direction of rotation (R1, R2) of the trolley(17) subsequent to at least one of a predetermined time period and apredetermined number of revolutions.
 8. A method according to claim 2wherein the steps of rotating the trolley through at least part of onerevolution in the first direction, then reversing the rotationaldirection, then rotating the trolley through at least part of onerevolution in the second direction, then reversing the direction ofrotation again together comprise rotating the oven trolley in one of thefirst and second directions (R1, R2) through 2-15 revolutions.
 9. Anarrangement according to claim 5 further comprising means (27) forcausing the drive means (20-26) to reverse the direction of rotation(R1, R2) of the trolley (17) subsequent to at least one of apredetermined time period and a predetermined number of revolutions. 10.An arrangement according to claim 6 further comprising means (27) forcausing the drive means (20-26) to reverse the direction of rotation(R1, R2) of the trolley (17) subsequent to at least one of apredetermined time period and a predetermined number of revolutions.